Safety control for oil burners



March 29, 1949. w. H. DE LANCEY SAFETY CONTROL FOR OIL BURNERS 3Sheets-Sheet 1 Filed Jan. 20, 1945 ATTORNEYS March 29, 1949. w H, DELANCEY 2,465,675

SAFETY CONTROL FOR OIL BURNERS 5 Sheets-Sheet 2 Filed Jan. 20. 1945 m MMm March 29, 1949. w H, DE LANCEY 2,465,675

SAFETY CONTROL FOR OIL BURNERS lllllllrl nnnf'rlnnnn INVENTOR Mifm/Kf/wcfy BY y. ya E e ATTORN EYS Patented Mar. 29, 1949 SAFETY CONTROL FOROIL BURNERS Warren H. De Lancey, Springeld, Mass., assignor to Gilbert &Barker Manufacturing Company,

West Springfield, Mass.,

Massachusetts a corporation o! Application January 20, 1945, Serial No.573,697

4 Claims. (Cl. 15S- 28) This invention relates to improvements in thesafety control mechanism of oil burners for stopping the burner onfailure of combustion.

Safety control mechanism oi this class is old and well known in the art.It generally, comprises a time switch, effective to open the circuit tothe burner motor in a predetermined time (say 30 seconds) after closingof such circuit by the room thermostat, or other control, provided thatcombustion does not occur, and a flame-responsive element or namedetector, which functions, on occurrence of combustion within thepredetermined time, to prevent the opening of the time switch. The flamedetector and the time switch mechanism may take various forms andoperate in various ways but the general functions accomplished are asstated.

It has been customary heretofore to mount the ame detector, which isgenerally a thermostat, outside of and separately from the air tube ofthe burner. It has thus been necessary to cut two holes in the wall ofthe rebox, one to accommodate the inner end of the air tube of theburner and the other to accommodate the burner thermostat or other flamedetector. The name-responsive element should be sighted at the burnername and yet it should be protected against all conditions which arelikely to adversely aect its operation and prevent it from functioningin the intended manner.

This invention has for one object to mount the flame detector in the airtube of the burner, locating it so that it is sighted at the ame and yetso that it is suiciently shielded from the air ow through the tube so asnot to be unduly inluenced by the presence or absence of a low ofrelatively cool air through said tube.

Another object of the invention is to locate the burner thermostat inand symmetrically of the air tube of the burner near the outlet end ofthe tube so that the thermostat does not project into the air stream asan obstruction and cannot therefore interfere with the desireduniformity of ilow of air to the fuel nozzle and cannot thereforedisturb the resulting i'lre.

The invention has for another object the provision of a complete safetycontrol mechanism, including a name-responsive element, a safetythermostat or time switch, and a heating element for the safetythermostat, all located in the air tube of the burner and shielded fromthe air iow through such tube.

Another object of the invention is to locate the 4iiame-responsiveelement, together with the safety thermostat, and its heating member ifdesired, in a recess in the inner end of the member. which supports theoil nozzle, so that said element is completely shielded from the air owthrough the tube and yet located back of the oil nozzle in confrontingrelation with the flame from the burner.

Another object of the invention is to utilize snap disc thermostats, onefor the ilamerespon i sive element and one for the time switchthermostat, and to mount these snap disc thermostats in opposed relationso that changes in ambient temperature balance out, leaving said elementto react solely to the presence o flame at the burner, whereby theflame-responsive element may be mounted in the air tube of the burnerand yet function satisfactorily.

The invention will be disclosed with reference to the accompanyingdrawings, in which- Fig. l is a sectional elevational view of an oilburner embodying one form of the invention;

Fig. 2 is a fragmentary sectional elevational view drawn to a largerscale and iilustrating the burner thermostat and safety switch;

Fig. 3 is an end elevational view of the burner;

Fig. 4 is a cross sectional view taken on the line -e of Fig. 1;

Fig. 5 is a sectional plan view taken on the line 5--5 of Fig. 4;

Fig. 6 is a fragmentary sectional view taken on the line @-5 of Fig. 3;

Figs. 7, 8 and 9 are sectional views taken on the v lines 1 1; 8 3; andS, respectively of Fig. 2.

Fig. l0 is a sectional plan, view showing the mounting of one of theignition electrodes; and

Fig. 11 is a wiring diagram of a burner control system for theinvention.

Referring to these drawings, the invention will be disclosed, by way ofillustrative example, in connection with an oil burner of the so-calledgun type. Such a burner has a pressure-atomizing nozzle l (Fig. 1) forproducing a spray of nely atomized oi! and a tube 2 through which airfor combustion is supplied to the oil spray. The forward and open end oftube 2 is adapted to be inserted in an opening in the wall of the reboxof the furnace. The mixture of air and oil is ignited by an electricspark occurring between the electrodes 3 and combustion occurs beyondthe end of tube 2 and in said firebox. The invention is not, however,limited to pressure atomization of the oil and is equally suitable f orany burner,

wherein an oil-spray-producing means of any type is surrounded by a tubethrough which air is supplied and wherein the open end of the tube isinserted in the wall of a rebox so that such open end confrontsthe flameresulting from com- --bustion of the oil and air mixture'.

sighted directly at the flame in the firebox, when` combustion occurs.And the burner thermostat must be shielded sufficiently from the airsupply flowing through tube 2 so as not to adversely eect itsfunctioning in the intended manner.

To secure these results, the burner thermostat` or ame detector ismounted back of the spray nozzle I and in coaxial relation therewith andthe air flow through the tube is directed away from the thermostat by amember 4, suitably supported in tube 2 in substantially coaxial relationtherewith. The oil supply conduit 5 passes through member 4 (Fig. 2) andthe nozzle I is threaded into the enlarged outer end 6 thereof. Themember 4, as shown in Fig. 1, is approximately cylindrical and its outerend, which lies nearest nozzle I, is provided with a cylindrical recess'I (,Figs. 2 and 8) having in its inner end Wall an arcuate groove 8.The outer end of recess 'I is counterbored to receive an annular snapdisk thermostat 9 which is held in place by a snap ring I or any othersuitable means. This snap disk 9 is the burner thermostat or flamedetector. This thermostat thus has an annular area which directly facesthe flame produced by the burner. At the same time the thermostat, beinglocated in the outer end of recess 'I is effectively shielded from theair flow through the tube 2.

In the form at present preferred, the safety thermostat switch and itsheating element are also located in the recess 'I. Mounted on conduit 5in coaxial relation therewith and seated against the inner end of recess'I is an annular disk II of suitable insulating material, such asBakelite for example, suitably held in place as by the screws II (Fig.7). This disk has three terminal buttons I2, I3 and I4, suitably fixedthereto, with extensions of the buttons I3 and I4 passing through thedisk and into the arcuate groove 8. An electric heater, comprising aresistance wire I5 of suitable material is connected to and supported bythe buttons I2 and I3. The disk II further has a circumferentiallygrooved hub I6 (Fig. 2) on which is mounted an annular snap diskthermostat I 1. A snap ring I8 in the groove in the hub holds disk I1 inplace axially while a flattened portion I9 (Fig. 9) on the hub I6flsengaged with a corresponding portion in the hole of the disk to preventthe latter from turning. The disk I 'I carries two contacts 20 and 2Ifor engagement with contacts I2 and I3 on disk II. The burner thermostat9 has fixed coaxially thereto, a metal sleeve 22 to which is alsosuitably fixed an annular member 23 of suitable insulating material. Asshown, the member 23 and the disk 9 are each held in place against ashoulder on the sleeve 22 by spinning one end of the sleeve against themember or disk as the case may be. The purpose of member 23 is to applypressure against the outer rim of thermostat I1 and hold its contacts 20and 2I engaged with the contacts I2 and I3, respectively, if combustionoccurs. The two thermostats 9 and I1 are normally bowed in oppositedirections,l as shown, whereby changes in -ambient temperature balanceout as they tend to move the disks equally but in opposite directions.The safety thermostat I1. when heated by the electric element I5.

tends'to move to the left as viewed in Figs. 1 and 2. If combustion doesnot occur, disk I'I will snap to the left and, through member 23, pressagainst the central part of disk 9 and cause the latter to snap to theleft. Thus, the hitherto engaged pairs of contacts 20, I2 and 2|, I3,will be disengaged and the burner circuit, later to be described, willbe opened. The burner thermostat 9, when subjected to the high heat ofthe flame produced by the'burner, tends to move toward the right withthe result that enough pressure is applied against thermostat I1 to holdit in its illustrated and switch-closing position even though thermostatI1 is fully heated by the heater I5.

The safety control described may be automatically or manually resetafter having stopped the burner motor on a failure of combustion. Thesethermostat disks may be made so as to automatically move back from theirabnormal to their normal position when the temperature fallssufliciently or they be so made as to remain in their abnormal positionsuntil manually moved back in any suitable way. Thermostat 9 may beconstructed in either of these ways although it is generally desired tocompel a manual resetting. This may be done by any suitable means. Forexample, a push rod 24 (Fig. 1), mounted as will later be described indetail, for movement longitudinally of tube 2, has one end accessiblefrom outside the rear end of the tube and the other end pivoted to oneend of a lever 25. The latter (Fig. 2) is pivoted intermediate its endsto member 4 and its inner end is adapted to engage and push member 23,inwardly,when

rod 24 is pushed inwardly, thereby pulling in.

wardly on disk 9 to snap it back from its left hand position int'o itsnormal and illustrated position and at the same 'time to snap backthermostat I'I and close the 'safety switch.

In Fig. 11, there is shown, by way of illustrative example, one form ofburner control system with which the safety control mechanism of thisinvention may be used. The electric motor, which causes air and oil tobe supplied to nozzle I and tube 2, respectively, is shown at 26 and theignition transformer which supplies high tension electricity to theelectrodes 31s shown at 21. This motor and transformerare connected inparallel in an electric circuit-say a volt circuit-comprising the wires28; 29 and 30 and a switch 3l, interposed between the wires 29 and 30.magnet 32, which also actuates a 'second switch 33. When the magnet 32is energized both switches will be closed and when it is deenergizedboth switches will open. The two switches and electromagnet form theso-called relay commonly referred to in oil burner controls. The magnet32 is included in a low voltage starting circuit from the secondary of atransformer 34. the primary of which is connected to the supply wires 23and 29. This starting' circuit is usually closed by a room thermostatswitch 35, 4although any other suitable means may be provided-for thepurpose. The starting circuit may be traced as follows, from oneterminalpfthesecondary of transformer 34 by a wire 36 to one terminal ofthe room thermostat 35. from the other terminal of the latter by a wire3,1 to button I2 ofthe safety control mechanism. through contact 20,disk I1 and'contact 2| to button I3, through heater I5 to button I4,thence by a wlr'eg33, to one terminal of magnet 32, and from the otherterminal of magnet 32 by'a wire 39 to the other Switch 3I is operated byan electroterminal of the secondary of transformer 34. When thermostatswitch closed, magnet 32 is energized and both switches 3| and 33 close.Closure of switch 3| starts motor 26 and energizes transformer 21 tosupply the ignition spark across the electrodes 3. Failure ofcombustion. as heretofore described, causes contacts 20 and 2| toseparate from buttons |2 and I3, respectively, and thus open the lowvoltage starting circuit described, whereupon the relay drops out,opening switch 3| and stopping the burner. Normally, thesafetythermostat would be sumciently heated by heater |5 to open thesafety switch I1 in about 30 seconds. If combustion occurs within thistime, the safety switch cannot open for the reason above described.Closure of switch 33 simply closes a second circuit of lower voltagesuiiicient to hold the relay closed once it is pulled in, butinsufficient to initially pull the relay in. In place of the wire 39,which connects one terminal of magnet 32 to an end terminal of thesecondary of transformer 34, wires and 4| with the interposed switch 33are provided to connect the same terminal of magnet 32 to a terminal ofsaid secondary which lies intermediate those already described. It willbe clear that both the starting and the holding circuits can be openedby the safety control mechanisms on failure of combustion. The inventionis not limited to use in the one form of control circuit hereindescribed. The one form of circuit described is merely one illustrativevexample of many control circuits with which the invention may readilybe used.

Referring now to the details of the exemplary apparatus, theburnerincludes a hollow frame comprising end members 40 and 4| (Fig. 1), and apair of abutting intermediate members 42 and 44 which are interposedbetween the end members. All these members are held together by a seriesof screws 43 (Figs. 4 and 5). This frame is supported by a post 45 froma pedestal 46, as indicated in Figs. l and 3. The tube 2 is iixed in anopening in the member 4| in axial alignment with a tubular extension 41of the member 40. A gasket 48 is interposed between the inner end ofextension 41 and the inner face of member 4| to make a tight jointbetween it and tube 2. The outer end of tubular extension 41 is closedby the ignition transformer 21 which is iixed toa plate 49, connected bya hinge pin 50 to member 40 and normally held in closed position by twoscrews 5| which pass through plate 49 and thread into member 40. Thehigh tension terminals of transformer 26 are springpressed buttons 52mounted in insulators 53 xed to the transformer. These button terminalslie inside the air tube near its outer and closed end. The outer end ofextension 41 is of larger diameter and receives a two armed spider 54,which spans the extension and has each outer end received between a pairof ribs 55 (Fig. 4) on the extension, thereby preventing the spider fromturning. The spider (Figs. 1, 3 and 4) has a central hollow tubularportion 56 which is closed at its outer end and has fixed in its innerend the outer end of the described oil conduit 5. A exible copper tube51, connected to the portion 56, extends out of the air tube through arecess 58 in member 40 and is connected to the oil pump-a union 51'being interposed in the connection. The ignition electrodes consist ofwires 3, each bent as best shown in Fig. l0 and inserted in alongitudinal hole in an insulator 60 with a right angularly bent portion3b lying in a radial groove in the insulator. A nut 58 threaded on theouter end of each wire 3 holds said bent portion in the groove and holdsthe wire against longitudinal movement in the insulator. Theseinsulators lie in recesses 6I in the sides of member 4 and are heldtogether by a metal strap 62 which is fixed as by screws 63 to member 4.This member 4 is supported near the inner end of tube 2 by three radialpins 64, the inner ends o f which are screw threaded into member 4 andthe outer ends of which b ear against the inner peripheral wall of tube2. The inner ends of the nuts 59 (Fig. 1) are engaged by the springpressed transformer terminals 52, whereby the member 4 is thrustinwardly in tube 2 until the outer ends of the spider arms 54 abut theshoulder 64 on extension 41.

The wires 31 and 38 are connected to the portions of their respectivebuttons I2 and I4 that project into the arcuate groove 8 and these wiresextend along the groove to a hole 65 (Fig. 2) through which they pass toa recess 66 (Figs. 1 and 2 in the bottom part of member 4. The wirespass through the tube 2 and include a separable connection comprising aplug 61 and socket 61' (Fig. 1), the former being suitably attached tothe member 4. These wires pass radially out of the rear end of the airtube 2 (Figs. 1 and 5) into a compartment 68 (Figs. 4 and 5) which isformed in the hollow frame member. Fixed in this compartment is a panel10, bearing the relay 32 and the transformer 34. This compartment isnormally closed by a cover 1I (Figs 1 and 5) having on one side spacedhinge lugs 12 (Fig. 5) bearing on ribs 13 on one wall of the compartment69 and having on the other side ya spring 14 which snaps into a recessin the other wall of the compartment to hold the cover closed.

The electric motor 26 (Fig. 3) is suitably secured to the frame member40,as by a series of screws 15. The wires 28 and 30 extend from thecompartment 69 through a groove 16 into the interior of the motorcasing. This motor (Fig. 1) has xed to the inner end of its shaft 11 afan 18. Within the motor casing are an oil pump, also driven from shaft4, an oil pressureregulating valve, a burner cut-ofi' valve for oil, anda strainer. These elements may, for exam.- ple, be arranged in the motorcasing as disclosed in the copending application of Virgil E. Duemler,Serial No. 529,048, filed April 1, 1944, now Patent No. 2,447,744granted August 24, 1948 and owned by the assignee of the presentapplication, or in any other suitable way.

The frame member 4|) is recessed to form a scroll chamber 19 (Fig. 4), aplenum chamber 80, which encompasses the air tube extension 41 and aconnecting passage 8| to deliverv air from the fan tangentially into theplenum chamber. The plates 42 and 44, which are respectively of metaland of sound deadening material (the latter serving also as a gasket),serve to close the scroll chamber except for a central air inlet `82(Fig. 1) from the space within the upper portion of the frame member 4|.Louvres 83 in the latter serve to admit air to said space and thus tothe fan. These plates 42 and 44 also form an inner wall for the passage8| but not for the plenum chamber 80. The inner end of the walls of suchchamber (Fig. 1) abut corresponding walls 84 on member 4I and providefor an-axially inward extension of the plenum chamber. Air from the fanwill thus be delivered into the plenum chamber and whirl around the airtube extension 41. The inner portion of the outer 4periphery ofextension 6l.

this sleeve (Fig. 6) are two axially-spaced radi-` in a whirling streamwhich is advanced through` tube 2 to the oil spray issuing from nozzleI.

To regulate the volume of air supplied to tube 2, a sleeve valve 86(Figs. 1 and 4) is mounted for axial sliding movement on the outer partof ally-outwardly extending lugs 8l which receive between them the lowerpart of a. piece 88, which as shown in Fig. 4 is shaped'roughly like thegure 3. A pin 89 (Fig. 4) passes freely through this piece 88 and hasits ends fixed one in each lug 9i. The upper part of piece 83 has ascrewthreaded hole extending axially therethrough. A screw 90 (Fig. 6)is engaged in such hole. At each end of this screw, is a plaincylindrical portion 9| of smaller diameter than the screw. Theseportions 9| are rotatably mounted one in each of the two frame membersdi and 4I. The outer end 9| of the screw is slotted (Fig. 3) to receivea screw driver and extends through an opening in the hinged andtransformer-supporting plate 69. By turning screw 90, the nut piecethereof. 'I'he weight of the longer and horizon- I tal arm of the bellcrank is enough to normally hold it in the illustrated position in whichit rests on one of the ribs 55. A slide 93 (Figs. 1

and 3) is slidably mounted in a groove 94 in` member, 40 and has anoutturned end 95 by` which it may be pushed upwardly. The upper end ofslide 93 (Fig. 1) is movable into the interior of extension 41 betweenthe transformer plate 49 and the bottom wall of the groove and canengage the horizontal arm of bellcrank 92` and move it to thrust rod 24forwardly and reset the burner thermostat, when necessary. The slide isheld in place by a smallstud 9B which passes through a vertical slot inthe slide.

l The mounting of the electrodes is believed to be important. Eachelectrode consists simply of a wire, having a straight portion 3a topass through the longitudinal hole in the insulator together with aright-angularly bent portion 3b at one end of the straight portion. Theportion Fixed to` radially projecting parts of each clamp are drawntogether to contract the clamp around its insulator so that the holdingforce is distributed around the periphery of the insulator instead ofbeing concentrated at one location or localized as heretofore. The samescrews, that serve to tighten the insulator clamps, also serve to bindthe strap to the support 4 and hold the insulators and electrodes inposition.

In the operation of the invention, when the room thermostat 35 closes ona demand for heat. a circuit is established through the relay 32 andthrough the safety switch I1, 20, 2i and the elec- 3b lits into one halfofva diametrical groove in l one end face of the insulator and preventsthe electrode from turning in the insulator and acts threaded into thenozzle support, such as 4. and

which press against the insulator either directly or through theintermediary of a bushing. The difilculty is to clamp the porcelaininsulators firmly in position without cracking them. Thepresentarrangemenr provides in the strap 62, two separate clamps, one toencompass each insulator, and 'by means of the screw 83 the Thismounting of an tric heater I5. The relay 32 closes switches 3| and 33,causing motor 26 to start and supply air and oil to tube 2 and nozzle I,respectively, and causing an ignition spark to be produced at electrodes3 to ignite the oil and air mixture issuing from tube 2. If combustionoccurs, the burner thermostat 9 will be heated and through sleeve 22 andmember 23 exert enough pressure on the thermostat Il and safety switchto prevent thelatter from opening. A failure of combustion. eitherinitially or at any time during operation of the motor 26, will enablethermostat 9 to cool and then snap to the left and allow the safetyswitch to open under the heat supplied 'by heater I5.

According to the invention, the burner thermostat is located in back ofthe oil nozzle and in coaxial relation therewith and as near as possiblein confronting relation with the burner flame so as to react to the heattherefrom and function eliciently as a llame detector. The location ofthe Vburner thermostat is of prime importance. What is desired, is aquick response of large magnitude following the occurrence of combustionand also following cessation of combustion. Cooling of the burnerthermostat by exposure of it to a flow of relatively cool air would inany event act to delay the response of the thermostat to occurrence ofcombustion and the magnitude of such response. And if the cooling effectwere great enough, the burner thermostat might never reach a temperaturehigh enough to operate at all. On cessation of combustion, if the burnerthermostat had ben exposed to a ilow of cool air, there would be a quickrise of temperature due to the heat from the combustion chamberfollowing cessation of air flow rather than the quick drop intemperature that is desired. Hence, it is important if a quick responseof large magnitude is to be secured on occurrence and on cessation ofcombustion, to shield the burner thermostat from the air now throughtube 2. It will be clear that the burner thermostat is completelyshielded from the air flow through tube 2. So also'is the thermostat ofthe safety switch.

The location of the Iburner thermostat symmetrically' of the air tubeand near the outlet end thereof is important all apart from theadvantage of shielding the thermostat from the current of cool air. Whenthe thermostat is located near the fuel nozzle and the outlet of the airtube. as it should be in order to have it function elciently as a flamedetector. it is essential that the thermostat be kept from interferingwith the air ow. If the thermostat should pro- 9 remains smooth anduniform and the nre undisturbed.

The invention thus provides means whereby a burner thermostat may belocated in the air tube of an oil burner and yet function properly witha quick and adequate response both to the occurrence and cessation ofcombustion.

I claim:

1. In an oil burner, a tube having inlet and outlet ends, the outlet endadapted to be inserted into an opening in the wall of a ilrebox, an oilsupply conduit supported in part in said tube, a spray nozzle in thetube on the outlet end of said conduit, electrically-operated means forforcing oil through said conduit and nozzle, means connected to theinlet end of said tube for forcing air therethrough to mix with the oilemitted from said nozzle, means for igniting the air and oil mixture, amember located adjacent but back of said nozzle and encompassing saidconduit, said member supported in said tube and spaced from theperipheral wall thereof and having a recess in that end which liesnearest the nozzle; and a safety control unit mounted in said recess andincluding a normally closed safety switch in circuit with saidelectrically-operated means and a snap disk thermostat to operate it-both located in the inner end of said recess, an electric element insaid recess for heating said disk and operable in a predetermined timeafter starting of said electrically-operated means if combustion doe'snot occur to cause the disk to open said switch and stop saidelectrically-operated means, and a second snap disk thermostat mountedin the outer end of said recess in opposed relation to the rst-nameddisk and in position to be exposed to the flame in the iirebox, saidsecond disk operable on occurrence of combustion to pre.

vent the first disk under the heat of said element from opening saidswitch.

2. In an oil burner, a tube having inlet and outlet ends, the outlet endadapted to be inserted into an opening in the wall of a rebox, an oilsupply conduit supported in part in said tube, a spray nozzle in thetube on the outlet end of said conduit, electrically-operated means forforcing oil through said conduit and nozzle, means connected to theinlet end of said tube for forcing air therethrough to mix with the oilemitted from said nozzle, means for igniting the air and oil mixture, amember located adjacent but back of said nozzle and encompassing saidconduit, said member supported in said tube and spaced from theperipheral wall thereof and having a recess in that end which liesnearest the nozzle; a safety control unit mounted in said recess andincluding a normally closed safety switch in circuit with saidelectrically-operated means and a snap disk thermostat to operate itboth located in the inner end of said recess, an electric element insaid recess for heating said disk and' operable in a predetermined timeafter starting of said electrically-operated means if combustion doesnot occur to cause the disk to open said switch and stop saidelectrically-operated means, a second snap disk thermostat'mounted inthe outer end of said recess in opposed relation to the first-named diskand in position to be exposed to the flame in the iirebox, said seconddisk operable on occurrence of combustion to prevent the nrst disk underthe heat of said element from opening said switch, and means manuallyoperable from outside said tube for resetting said disks and closingsaid switch.

3. In an oil burner, oi the type having a tube which has an opendelivery end adapted for insertion in an opening in the wall of theflrebox and through which tube air for combustion iiows. an oil supplypipe terminating with a part which is supported in said tube insubstantially coaxial relation therewith and which has an oil-atomizingnozzle on its delivery end, a pump for forcing oil through said pipe,and a motor for driving the fan and pump; a casing having a cylindricalperipheral wall, a back wall and an opening at the front; said casingbeing mounted on said part of the oil pipe in back of said nozzle, saidpart of the conduit passing through said back wall into the casing andout through the front of the casing with the peripheral wall of theconduit spaced from the peripheral Wall of the casing forming an annularrecess, the front opening of said casing facing the delivery end of saidtube in position to be exposed to the radiant heat from the flame in therebox, an annular snap-disk thermostat located in said annular recess ofthe casing in encompassing relation with said part of the oil pipe, saidthermostat being exposed through said front opening to said radiant heatand shielded by the peripheral wall and back wall of the casing from theair ow through said tube, and means controlled by said thermostat andoperable on failure of combustion to stop said motor.

4. In an oil burner, of the type having a tube which has an opendelivery end adapted for insertion in. an opening in the wall of a reboxand through which tube air for combustion iiows, an oil supply pipeterminating with a part which is supported in said tube in substantiallycoaxial relation therewith and which has an oil-atomizing nozzle on itsdelivery end, a pump for forcing oil through said pipe, and a motor fordriving the fan and pump; a casing having a cylindrical peripheral wall,a back wall and an opening at the front; said casing being mounted onsaid part of the conduit passing through said back Wall into the casingand out through the front of the casing with the peripheral Wall of theconduit spaced from the peripheral Wall of the casing forming an annularrecess, the front opening of said casing facing the delivery end of saidtube in position to be exposed to the radiant heat from the flame in therebox, an annular snap-disk thermostat located in said annular recess ofthe casing in encompassing relation with said part of the oil pipe, saidthermostat be ing mounted near the front of said casing and exposedthrough said front opening to said radiant heat, a second annular snapdisk thermostat mounted in said annular recess in encompassing relationwith said part of the oil pipe and located rearwardly of the firstthermostat, an electric heater in said recess for the second thermostat,a control circuit for the burner motor including a safety switch locatedin said recess and operable by the second thermostat after the latterhas been heated for a predetermined time interval to open and stop themotor, the first thermostat being connected to the second thermostat andoperable on occurrence of combustion within said interval to dominatethe second thermostat and prevent it from opening said switch, saidthermostats being reversely arranged to compensate for changes inambient temperature, said thermostats being shielded by the peripheralwall and back wall of said casing from the air flow through said tube.

WARREN H. DE LANCEY.

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